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Old 10-10-2010, 10:58 AM
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CAM HELP! Comp Cams XR276HR In a sbc 383

hey hotrodders! i was planning to install the comp cams Xr 276 HR camshaft in my sbc 383. i have 10.1 compression, AFR 180 eliminator heads, and an air gap manifold with a 650 proform race series carb. my question is does this cam have any lope in a 383. has anyone put this cam in a 383 and have a sound clip? btw i have 3 inch exhaust, hooker headers with 1 5/8 primaries and an x pipe. The reason why i think i wont hear much with this cam would be because this cam has 59 degrees of overlap. please any other cam suggestions would be awesome. Im looking for a cam with a choppy/ mild rough idle.

The XR276HR has the following specs
276/282 duration @0.006
224/230 duration @0.050 W/ 502 &510 lift and 59 degress overlap

MY other cam options were the Comp Cams 280HR , 286hr, and the xr282hr

thanks for your time, Mark

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Old 10-10-2010, 11:52 AM
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Well IMO it is not always wise to install a cam based upon the lope/sound but it is your build, i assume that you did some research to match things up anyway and that combo looks OK with the 276, it should be a "fair idle" certainly noticable but not too lumpy, what is the LSA? on the 276.
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Old 10-10-2010, 12:00 PM
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the lsa is 110. i dont want a really rough idle. my last sbc 383 motor had a rough idle due to it having 90 degrees overlap! It was a hyd roller 306/306 at 0.006 and 230 at 0.050 with 480 lift. the way i look at it as long as i dont go over 70 degrees i'll get a good prostreet sound without killing the daily drive.
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Old 10-10-2010, 12:12 PM
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Yeah the LSA will have an effect on the idle quailty and the 110 altough not being on the low side will give it more lump than say a 112-114

I don't know about a "pro street" sound but it should be making a statement at a red light anyhow , good luck with it, maybe post/link us with a sound clip when its done.
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Old 10-10-2010, 12:21 PM
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Go to the AFR website, they know what works. There are a bunch of different combos and dyno test in the magazine artcles.
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Old 10-10-2010, 12:24 PM
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You have a nice set of heads but do not have enough valve lift to
see the benefit.

Call Comp cams on the phone and order a custom grind cam.
The Comp Cams Hyd roller Cam lobe is #3015 intake and exhaust. Grind on a 108LSA
Install on 106 intake C/L.

Use 1.6 rockers. Follow comp cams recommendations on the valve springs.
(Beehive Ovate)

The carb is too small.

274 274 224-224 .573"-.573" (1.6rocker) 108
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Old 10-10-2010, 12:37 PM
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http://www.airflowresearch.com/chevy_dyno.php
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Old 10-10-2010, 12:57 PM
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Thanks a lot Custom10 , a lot of good info. the carb actually flows about 725cfm due to the milled choke. I saw the dyno sheets but those the older 180 heads, i dont think that those heads flow as well as the eliminator series 180s. As far as lift goes on the flow chart the flow does not increase a huge lot from 500 to 550 or even 600 only 1 cfm on intake and 2 cfm on exhaust from 500 lift to 600. What do you guys think, would a 1.6 do a better job. i currently bought 1.5 prw full roller rockers but i can exchange if i get the green light!
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Old 10-10-2010, 02:40 PM
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I have this exact cam in my 406, but my heads aren't as nice (Vortec). The idle is noticeably lumpy, but not so much that I would call it choppy, though I do have a few more cubes than you do. It idles with good vacuum and runs really good on the street. I haven't hit the strip yet. This cam was recommended by Comp for my setup.

Vortec heads with roller rockers (1.5 was recommended by Comp)
2600 Stall converter for my 700R4 trans and 3.73 gears
770cfm Holley
Edelbrock RPM Air Gap intake
9.8:1 compression
5.7 rods connected to KB Hyperutectic pistons
3" single exhaust with muffler (no cat)
1 5/8" mid length headers (Thorley)
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Old 10-10-2010, 03:04 PM
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Quote:
Originally Posted by F-BIRD'88
You have a nice set of heads but do not have enough valve lift to
see the benefit.

Call Comp cams on the phone and order a custom grind cam.
The Comp Cams Hyd roller Cam lobe is #3015 intake and exhaust. Grind on a 108LSA
Install on 106 intake C/L.

Use 1.6 rockers. Follow comp cams recommendations on the valve springs.
(Beehive Ovate)

The carb is too small.

274 274 224-224 .573"-.573" (1.6rocker) 108
Thats not a bad cam selection for those heads as the AFR heads really need no slpit as the intake and exhaust ratio is really good.

With an air gap intake I really would not expect to see a big differance going to a 750 carb as that cam is not really that big to move that much air through a 180CC runner head.
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Old 10-10-2010, 03:34 PM
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hey pro-tuner my setup also is running a 700r4 pro built trans but i have 4.11s in a 9" rear end. this is all going in a 1984 el camino so i hope my 23-2500 daaco converter will still work. can you upload or email me a clip of how it sounds? if it sounds as good as you describe in a 400 block then it should sound a little big in a 383. my exhaust is just long-tube hooker headers 3'' all the way out, 3" x-pipe and dual one chamber flowmasters with turndowns that dump under the rearend.
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Old 10-10-2010, 03:44 PM
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I'm not quite sure how to post a sound, but I'll try to figure it out. If nothing else, I should be able to post a video link after I get one.

I could be wrong, but dual 3" sounds a little on the big side to me. Maybe someone with more experience can chime in on that though.

Having dual exhaust will sound quite a bit different than my single. Should sound good though.

If I had to do the converter over again, I would go to a 2800-3000.
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Old 10-10-2010, 04:43 PM
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i would apperceiate it a lot if you can help me out with that sound clip! Thanks Mark
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Old 10-10-2010, 06:32 PM
406cu.in. of tire smokin' fun
 

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I can't figure out how to upload an audio file, but if you PM me your email address I can send it. It's captured by cell phone, so please excuse the quality. It should give you a good general idea though.

If anyone knows how, please help me out. Evidently YouTube will only process audio if there is video attached.
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Old 10-10-2010, 06:51 PM
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my email is chevyelcamino1984@yahoo.com, thanks Mark
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